Tetrazaindenes and photographic emulsions containing them



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This invention relates to fog inhibiting agents and stabilizers for photographic emulsions and to photographic emulsions containing them.

It is well known that photographic emulsions on storage tend to lose sensitivity and to become spontaneously developabie without exposure to light. There is normally a detectable amount of the silver salt reduced during development in the areas where no exposure was given; this is commonly called fog, and sometimes called chemical fog where it is necessary to distinguish between it and the effects of accidental exposure to radiation; in this invention, we are not concerned with the latter.

Fog depends both on the emulsion and the conditions of development; for a given emulsion it increases with the degree of development. With constant development conditions, it tends to increase with time, temperature and relative humidity of storage conditions; it is common practice to make accelerated tests of the stability of photographic emulsions by storage at increased temperature or humidity, or both. It is, of course, desirable to have emulsions as stable as possible under the conditions of high temperature and humidity which may occur in tropical climates, for example. Fog usually appears over the whole area of the sensitive coating, but when severe, it frequently is non-uniform. Fog may also be caused by exposure to chemicals, for example, hydrogen sulfide and other reactive sulfur compounds, hydrogen peroxide vapor, and strongly reducing materials. While antifoggants and stabilizers may protect, to some extent, against such effects, it is normally understood that an antifoggant protects against spontaneous growth of fog during prolonged storage or storage at high temperatures and humidities, or during development to maximum contrast and speed, or both.

it is, therefore, an object of the present invention to provide a method for stabilizing photographic emulsions. A further object is to provide a means for reducing the fog produced upon keeping of such emulsions which have r been sensitized, especially emulsions stored under tropical or other adverse conditions. A still further object is to provide a means for stabilizing the speed and contrast of sensitized photographic emulsions. Other objects will become apparent from a consideration of the following description and examples.

According to our invention, we provide a method for stabilizing photographic silver halide emulsions by incorporating therein a compound selected from those represented by the following general formula:

R2 N N atent and R represents a hydrogen atom, an alkyl group (such as methyl, ethyl, etc.), or an aryl group (such as phenyl, tolyl, etc., especially a mononuclear aromatic group of the benzene series). The compounds represented by Formula I above wherein R represents a methyl group and R represents a hydrogen atom have been found to be especially useful in practicing our invention. The compounds selected from those represented 1 by Formula I above (R is hydroxyl) can advantageously be prepared by condensing 3-amino-5-hydroxy-methyl- 1,2,4-triazole together with an ester selected from those represented by the following general formula: (II) (I) R2 R1- CHCOORa wherein R and R each has the values given above'and R represents a lower alkyl group (such as methyl, ethyl, etc). Such a method hasbeen previously described in Heimbach and Kelly U. S. Patent 2,444,604, issued July 6, 1948, and Berichte, vol. 42, page 4643, and vol. 43, pages 378380. The compounds selected [from those represented by Formula I above wherein R is a halogen atom can advantageously be prepared by heating together a compound selected from those represented by Formula I above wherein R is a hydroxyl group and a phosphoryl halide, such as phosphoryl chloride. Illustrative examples of these methods are given below.

Compounds selected from Formula I above which can be used in our invention in clude those represented by the following formulas:

(1) mo W TCHzOH 0H 4-hydroxy-2-l1ydr0xymethyl-6-methyl-1,3,3a,7-tetrazaindene 2 N N H3O Y T011201 tel H 2-chloromethyl--hydroxy-6-methyl-1,3,3n,7-tetrazalndene H509 NYNTCHQOH H 4-hydroxy-2-hydroxymethyl-6-pheny1-l,3,3a,7-tetrazaindene 5-ethyl-4-hydroxy-2-hydroxymethy1-6-methyl-1,3,321,7 tetrazaindene (5 N N HtCt HsC N l 4-11ydroxy2-bydroxymethyl-G-methyl-5-phenyl-1,3,3a,7-

tetrazaindene those represented by The antifoggant compounds represented by Formula I can be employed in emulsions which have been sensitized optically or chemically, or emulsions which have not been so sensitized. It is known that the efiective sensitivity of photographic silver halide emulsions can be increased by adding to them derivatives of alkylene oxides, such as ethylene oxide polymers having molecular weights of 300 or more. The practical value of these compounds is severely limited by their tendency to increase fog on storage of the photographic film, especially storage at elevated temperatures and humidity. It has been found difiicult to control this by the antifoggants commonly available without using quantities of antifoggants which partly neutralize the speed increase obtained from the alkylene oxide derivatives.

The alkylene oxide polymers used to sensitize the emulsions can be of various types. The alkylene oxides from which the polymers are derived contain from 2 to 4 carbon atoms, e. g., ethylene oxide, propylene oxide and butylene oxide. The preparation of polymers from these compounds is described in Ellis, The Chemistry of Synthetic Resins (1935), pages 990 to 994. These compounds are also referred to as polyalkylene glycols and their use as sensitizers for silver halide emulsions is described in U. S. Patents 2,423,549 and 2,441,389. Ethylene oxide polymers have been found to be especially advantageous in practicing our invention.

Various derivatives of alkylene oxides may also be used to sensitize the silver halide emulsions, e. g., condensation products of alkylene oxide with glycols, such as those having from 8 to 18 carbon atoms, as described in U. S. Patent 2,240,472 and British Patent 443,559, as well as condensation products of alkylene oxides with aliphatic alcohols, aliphatic acids and aliphatic amines, that is, polyalkylene ethers, esters and amides, the preparation of which is described in U. S. Patent 1,970,- 578, condensation products of alkylene oxides with phenols, also described in U. S. Patent 1,970,578, and condensation products of alkylene oxides with hexitol ring dehydration products, as described in U. S. Patent 2,400,532.

In each case the polyalkylene oxide or derivative of alkylene oxide should have a molecular weight of at least 300. Condensation products of ethylene oxide with long chain alcohols should have a molecular weight of about 700; other derivatives may have a molecular weight of 1500 to 4000 or more.

The principal purpose of our invention is to provide a means for maintaining the sensitivity and fog of silver halide emulsions at or close to initial optimum values under conditions of high temperature or high humidity, or both. Preferably, the antifoggants of our invention are added to the emulsion at any stage during the process of manufacture prior to coating the emulsion. The antifoggants can be added to the emulsion in solution in water or any convenient solvent not injurious to the emulsion, such as lower aliphatic alcohols.

The solutions of antifoggants which we employ when added in suitable concentration before coating to unsensitized or optically sensitized silver halide emulsions usually do not appreciably affect the sensitivity and fog when measurements are made soon after coating. However, when sensitometric measurements are made after appreciable intervals of time under tropical or dry conditions of storage at elevated temperatures, the antifoggants do stabilize speed and maintain fog at a low level.

The alkylene oxide derivatives which can be used to sensitize the emulsions can be illustrated by the following specific examples, although our invention is in no way limited to the use of these specific compounds.

HO CH CH O CH Cl-l o ,CH CH OI-I Polyethylene oxide Di- (polyethylene-glycoxy) decane HOCH CH O(CH CH O),,CH CH OC H Polyethylene oxide oleyl ether where n=an integer greater than about 10.

The preparation of silver halide emulsions involves three separate operations: (1) the emulsification and digestion or ripening of the silver halide, (2) the freeing of the emulsion from aqueous soluble salts usually by washing, (3) the second digestion or after-ripening to obtain increased sensitivity (Mees, The Theory of the Photographic Process, 1942, page 3). The fog inhibiting agents can be added at any stage, preferably after the final digestion.

The photographic emulsions which we use are of the developing-out type and best results have been obtained with gelatino-silver bromoiodide emulsions. However, emulsions of varying halide content can be used.

The emulsions can be chemically sensitized by any of the accepted procedures. The emulsions can be digested with naturally active gelatin, or sulfur compounds may be added such as those described in Sheppard U. S. Patent 1,574,944 and U. S. 1,623,499, and Sheppard and Brigham U. S. Patent 2,410,689.

The emulsions can also be treated with salts of the noble metals such as ruthenium, rhodium, palladium, iridium and platinum, all of which belong to group VIII of the periodic table of elements and have an atomic weight greater than 100. Representative compounds are ammonium chloropalladate, potassium chloroplatinate and sodium chloropalladite, which are used for sensitizing in amounts below that which produces any substantial fog inhibition, as described in Smith and Trivelli U. S. Patent 2,448,060, and as antifoggants in higher amounts, as described in Trivelli and Smith U. S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts as described in Waller and Dodd U. S. Patent 2,399,083, or stabilized with gold salts as described in Damschroder U. S. Patent 2,597,856 and Yutzy and Leermakers U. S. Patent 2,597,915. Suitable compounds are potassium chloroaurite, potassium aurithiocyanate, potassium chloroaurate, auric trichloride and 2- aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agents, such as stannous salts (Carroll U. S. Patent 2,487,850), polyamines such as diethylene triamine (Lowe and Jones U. S. Patent 2,518,698), polyamines such as spermine (Lowe and Allan U. S. Patent 2,521,925), or bis-([i-aminoethyl) sulfide and its water-soluble salts (Lowe and Jones U. S. Patent 2,521,926).

The emulsions can also be stabilized with the mercury compounds of Allen, Byers and Murray U. S. application Serial No. 319,611 (now U. S. Patent 2,728,663, issued December 27, 1955); Carroll and Murray U. S. application Serial No. 319,612 (now U. S. Patent 2,728,664, issued December 27, 1955); and Leubner and Murray U. S. application Serial No. 319,613 (now U. S. Patent 2,728,665, issued December 27, 1955), all filed November 8, 1952.

The antifoggants of our invention alone, or in combination with polyalkylene oxides or their derivatives, are. effective in the presence or absence of optical sensitizing dyes. Since optical sensitizing can affect stability of emulsions with respect to sensitivity, fog and latent image changes, the action of the antifoggants is not completely independent of optical sensitizing or other emulsion variables. We have found, however, that both unsensitized emulsions and emulsions sensitized with cyanine or merocyanine dyes, or both, can be treated with the antifoggant compounds represented by Formula I above.

The quantity of antifoggaut compound employed can In a manner similar to that illustrated in the above examples, other compounds selected from those represented by Formula I .can be used to stabilize photographic silver halide emulsions, either in the presence or abbe varied, depending upon the particular silver halide 5 sence of chemical sensitizers. employed, degree of ripening, presence or absence of We have also found that compounds corresponding to other emulsion addenda, etc. In general, the quantity of those of Formula I wherein R represents a formamidinoantifoggant mu vary from about 0.1 to 10 grams per thio (hydrochloride) group can be employed in photogram mole of silver halide in the emulsion. These graph1c silver halide emulsions, though less advantageousamounts can be used in combination with one or more 10 ly than the compounds represented by Formula I. of the chemical sensitizing and stabilizing agents listed Instead of incorporating the antifoggants in the photoabove. graphic silver halide emulsion, these antifoggants can be The stabilizing action alforded by the antifoggants of incorporated 1n a colloid layer, such as a gelatin overour invention was determined by incubation of the coating layer or inter'layer, in contact with the emulsion. emulsions for a period of two weeks at 120 F. and at The fog-inhibiting agents which we have described can constant humidity. The speeds were measured in terms be used in various kinds of photographic emulsions. In of 30/E where E is die exposure required to produce a addition to being useful in non-sensitrzed emulsions, they density of 0.2 above fog. The antifoggants were added can also be used in orthochromatic, panchromatic, and to a panchromatically sensitized, high speed silver bromi- X-ray emulsions. If used with sensitizing dyes they can odide emulsion which had been chemically sensitized with be added to the emulsion before or after the dyes are a sulfur compound, such as described in Sheppard U. S. added. Various silver halides can be used as the light- Patent 1,574,944 and potassium chloroaurate. The emulsensitive material, lncludmg silver bromide, silver iodide, sions were coated on a cellulose acetate support and the silver chloride, silver bromiodide, silver chlorobromide, coatings exposed on an Eastman I(b) Sensitometer silver chlorobromiodide, etc. The antifoggants of our and processed for four minutes in a developer (Kodak 25 invention can be used in emulsions intended for color D-19.) having the following composition: photography, for example, emulsions containing colora forming couplers, or emulsions to be developed by solu- Water about 500 tions containing couplers.

N'ntethyl'p'ammopilenol sulfate The polyethylene oxide polymers used in th emulsiqns deslccated "5-- according to our invention can be prepared either 'by fiydyoqmnone p g polymerizing ethylene oxide in the presence of aliphatic Sodlm? a 'monchydmte "jg-- acids, aliphatic amines, or phenols, or by reacting the poly- Potasslum brom'de g merized polyethylene oxide with aliphatic acids, acid Cold Water to make one hterchlorides, or esters,.whic;h produces similar products.

Alternatively, the exposed coatings werepuocessed for The dlspersm? agents b5 gelatin or i colloids five minutes in Kodak D1950 developer hafing the such as collodion, albumen, cellulose derivatives, synlowing composition. thetie resins, etc.

The following examples will illustrate the method re- NmethYLPaminoPhenol lf t 25 f rred to b ve of preparing the compounds of Formula Hydmqu'inone 25 -40 I, or the corresponding compounds wherein R is a form- Sodium Sulfite desiccated 300 anudinothiogroup. Other somewhat similar compounds Sodium metaomte 101) are shown in Examples 12 and :13 below.

Potassium bmmid" Example 7.--3-amino-S-hydroxymethyl-I,2,4-triaz0le Water to make one liter.

The results of these tests for speed, gamma and fog, HOCHPC before and after incubation of each of .the samples, are 1 NH .HO 011200011 given in the following table. In the table, the same batch of emulsion was employed in Examples 1 and 2, the same A mixture of 272 g. (two moles) of aminoguanidine bibatch of emulsion was employed in Examples 3 and 4 59 carbonate, 440 ml. of percent aqueous glycolic acid and the same batch of emulsion was employed in Ex- (four moles), and two m1. of concentrated nitr1c acid amples 5 and 6. was refluxed for 24 .hours, then cooled well and filtered.

TABLE I Conoen- Fresh Tests 2 Wks., -F. C d l iie o lfx n Emma ompoun filLg: p lfayed Rel. Gamma. Fog Rel. Gamma Fog Speed Speed 3,150 1.49 .14 2,850 1.16 .22 3,600 1.47 .12 3,350 1.31 .15 3,850 1.44 .11 3,600 1.82 .14 4, 750 1.10 .14 5, 450 0.94 .20 4,750 1.04 .14 5,700 0.91 .16 5,850 .94 .20 emu 0.80 .20 0.9 5,150 0.92 .11 5,600 0.81 .17 0.75 250 0.86 .15 6,250 0.63 .29 3:5 8,650 0.82 .14 8,450 0.66 .19 3:3 8,650 0.79, .14 7,700 0.61, .14 3,600 1.30 .16 3,600 1.12 .20 0 9 3,850 1.43 .14 3,700 1.12 .17 0.75 5,200 1.21 .21 6,250 0.88 -27 3:5 0o.-.. 5,450 1.25 .16 5,850 1.03. .21

In the above table: -A=4-hydroxy-2-hydroxymethyI-Gmethyl-l,3,3a,7-teh'azalndene- B=polyethylene glyeol ether of clay] alcohol; O=2-ehloromethyl-4-hydroxy-6-methyl-1,3,8a,7-temzaim1el1e.

5.3; N, 29.5. Found: C, 32.0; H, 5.3; N, 31.4.

Example 8.4-hydroxy-2-hydroxymethyl-6-methyl-1,3, 3:1,7-tetrazaindene mo /N Y 011.011

ll- NN A mixture of 50 g. of the compound described above (Example'l), ml. of glacial acetic acid, and 250 ml. of ethyl acetoacetate was heated on the steam cone overnight. Cooled', filtered, and the solid recrystallized from 400 ml. of .6 N,hydrochloric acid; 50 g., 63 percent, of

solid, P. 268-270 C. were obtained.

Analysis. Calcd: C, 46.6; H, C, 45.8; H, 4.8; N, 31.1.

Crystallization from water yielded the M.-P. 227'- 229";-C.

Analysis.Calcd: C, 44.5; H, 4.8; N, 29.7. Found: C, 44.5; H, 4.7; N, 29.8.

Exam pie 9. 2-chlor0methyl-4-hydr0xy-6-methyl-1,3,

" 3a',7tetraz 'ndene mc qIiIomo1 Twenty-five g. of the substance described above (Example 8) was refluxed with phosphoryl chloride for one hour, evaporated to dryness at 90 C. and mm., and treated with ice water. The mixture was treated with a little cyclohexanone and some chloroform, and allowed to warm up to room temperature during several hours, after which the product, at first gluey, had become a white powder. It was filtered and dried; 13.8 g., 48 percent, of the hemihydrate, M. P. 260-263 C., was obtained. I v

Analysis.,-Calcd' for C H ClN O.%H-,,0: C, 40.6; H, 3.9; CI, 17.2;N, 27.1. Found: C, 39.5; H, 3.9; Cl, 17.4; N, 27.9.

Crystallization from 6 N hydrochloric acid yielded the anhydrous compound, M. P. 265266 C.

Analysis.Calcd: C, 42.4; H, 3.5; Cl, 17.9; N, 28.2. Found: C, 42.4; H, 3.7.

Example 10.-2-formamidinothi0methyl-4-hydr0xy-6- methyl-1,3,3a,7-tetrazaindene Two grams of 2-chloromethyl-4-hydroxy-6-methyltetrazaindene and one gram of thiourea in 100 cc. of ethanol were refluxed 8 hours. Three hundred cc. more alcohol were added, heated to boiling, and filtered. The residue recrystallized from 70 cc. of aqueous ethanol, yielding 0.6 gram, M. P. 262-264 C. dec.

Analysis.Calcd: C H ClN,O S (111. wt. 293): C, 32.8; H, 4.4; N, 29.4; S, 11.0. Found: C, 33.3; H, 4.6; N, 29.4; S, 11.3.

4.5; N, 31.1. Found:

hemihydrate,

8 Example 11 4 chloro 2 chloromethyl 6 methyl l,3,3a,7-

Example 12.-2-chlor0methyl-6-methyl-4-m0rph0lino- 1,3,3a,7-tetrazaindene Hz H:

A mixture of 20 grams of the crude dichloro derivative, (Example 11), 350 cc. of ethanol, and 18 cc. of morpholine was refluxed 2 hours; enough water was added to give complete solution, then filtered and cooled. Avwhite solid separated, 11 grams, 47 percent, M. P., 204-205 .C.

Analysis.Calcd: (C H ClN O, 111. wt. 268): C,

49.4; H, 5.2. Found: C, 49.5, 49.1; H, 5.3, 5.7."

Example 13.-Bis(2 formamidirwthiomethyl-6-methyl- 1,3,3a,7-tetrazainden-4-yl)-sulfide dihydrochloride dihydrate A mixture of 20 grams of the dichloro derivative (Example ll), 7.7 grams of thiourea, and 350 cc. of ethanol was refluxed 2 hours; evaporated to dryness, crystallized from ethanol-ethyl acetate, then several times from ethanol, finally yielding 2.2 grams of pale yellow solid, M. P., 144-145 C. (9 percent yield).

Analysis.Calcd: (C H Cl N S O- m. wt. 582): C, 33.0; H, 4.1; N, 28.9; S, 16.5. Found: C, 34.0; H, 3.8; N, 28.9; S, 16.7.

What we claim as our invention and desire secured by Letters Patent of the United States is:

1. A photographic sliver halide emulsion containing a compound selected from those represented by the following general formula:

iigir wherein R represents a member selected from the group consisting of a hydroxyl group and a chlorine atom, R represents a member selected from the group consisting of a methyl group and a mononuclear aromatic group of the benzene series, and R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms, and a mononuclear aromatic group of the benzene series.

2. A photographic silver halide emulsion as defined in claim 1 wherein the silver halide is silver bromiodide. P

3. A photographic silver halide emulsion containing a compound selected from those represented by the following general formula:

wherein R represents a member selected from the group consisting of a hydroxyl group and a chlorine atom and R represents a member selected from the group consisting of a hydrogen atom, and alkyl group containing from 1 to 2 carbon atoms, and a mononuclear aromatic group of the benzene series.

4. A photographic silver halide emulsion as defined in claim 4 wherein the silver halide is silver bromiodide.

5. A photographic silver halide emulsion containing 4- hydroxy 2 hydroxymethyl 6 methyl 1,3,3a,7- tetrazaindene.

6. A photographic silver bromiodide emulsion containing 4 hydroxy 2 hydroxymethyl 6 methyl 1,3,3a,7- tetrazaindene.

7. A photographic silve halide emulsion containing 2- chloromethyl 4 hydroxy 6 methyl 1,3,3a,7 tetrazaindene.

8. A photographic silve bromiodide emulsion containing 2 chloromethyl 4 hydroxy 6 methyl 1,3,3a,7- tctrazaindene.

9. A photographic silver halide emulsion sensitized with an alkylene oxide polymer selected from the class consisting of condensation products of an alkylene oxide wherein R represents a member selected from the group consisting of a hydroxyl group and a chlorine atom, R represents a member selected from the group consisting of a methyl group and a mononuclear aromatic group of the benzene series, and R represents a member selected from the group consisting of a hydrogen atom, an alkyl group containing from 1 to 2 carbon atoms, and a mononuclear aromatic group of the benzene series.

References Cited in the file of this patent UNITED STATES PATENTS 2,407,204 English et a1. Sept. 3, 1946 2,449,225 Heimbach et a1. Sept. 14, 1948 2,519,715 Stewart Aug. 22, 1950 2,657,136 Knott et a1. Oct. 27, 1953 2,673,152 Allen et a1. Mar. 23, 1954 

1. A PHOTOGRAPHIC SILVER HALIDE EMULSION CONTAINING A COMPOUND SELECTED FROM THOSE REPRESENTED BY THE FOLLOWING GENERAL FORMULA: 